Available-For-Sale Securities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2011	Dec. 31, 2010
Available-For-Sale Securities
Available-for-sale securities, debt maturity date	2027
U.S. Government-sponsored agency securities, to include shareholder equity	10.00%
Securities, carrying value	$ 1,100	$ 876

The fair value of available-for-sale securities that serve as collateral for borrowings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 01-6

-Paragraph 13

-Subparagraph i

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6965416&loc=d3e5086-111524

Name:	us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant